Semiconductor device and fabrication method therefor

ABSTRACT

A method of fabricating a semiconductor device. The method includes forming a dummy structure over a substrate, forming conductive features on opposite sides of the dummy gate structure, removing the dummy structure and a portion of the substrate beneath the dummy gate structure to form a trench, and filling the trench with a dielectric material.

BACKGROUND

Capacitors are components for many data manipulation and storageapplications. In general, a capacitor includes two conductive electrodesseparated by an insulator. Various capacitors are used for a myriad ofpurposes in modern integrated circuits (ICs). For example, in avertically-oriented capacitor such as a metal-insulator-metal (MIM)capacitor, a dielectric material is sandwiched between two metal layersor between a polysilicon layer and a metal layer. As design rulesshrink; however, capacitance values decrease because dimensions of themetal layer or the polysilicon layer decreases. The capacitance of acapacitor depends on a thickness of the dielectric material. A thindielectric material results in the capacitor having a high capacitance.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are illustrated by way of example, and not bylimitation, in the figures of the accompanying drawings, whereinelements having the same reference numeral designations represent likeelements throughout. It is emphasized that, in accordance with standardpractice in the industry various features may not be drawn to scale andare used for illustration purposes only. In fact, the dimensions ofvarious features in the drawings may be arbitrarily increased or reducedfor clarity of discussion.

FIG. 1 is a flowchart of a method of fabricating a semiconductor deviceincluding a capacitor in accordance with one or more embodiments.

FIGS. 2A-2H are cross-sectional views of a semiconductor device having acapacitor at various stages of fabrication in accordance with one ormore embodiments.

FIG. 3A is a schematic diagram of a semiconductor device in accordancewith one or more embodiments.

FIG. 3B is a cross-sectional view of the semiconductor device of FIG. 3Ain accordance with one or more embodiments.

FIG. 4A is a schematic diagram of a semiconductor device in accordancewith one or more embodiments.

FIG. 4B is a cross-sectional view of the semiconductor device of FIG. 4Ain accordance with one or more embodiments.

DETAILED DESCRIPTION

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of theinvention. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Forexample, the formation of a first feature over or on a second feature inthe description that follows may include embodiments in which the firstand second features are formed in direct contact, and may also includeembodiments in which additional features may be formed between the firstand second features, such that the first and second features may not bein direct contact. Various features may be arbitrarily drawn indifferent scales for simplicity and clarity. In addition, the presentdisclosure may repeat reference numerals and/or letters in the variousexamples. This repetition is for the purpose of simplicity and clarityand does not in itself dictate a relationship between the variousembodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

A capacitance of a capacitor depends upon a structure of the capacitor.In some approaches for forming capacitors, uneven insulating layersresult in excessive capacitance variation for different capacitors inintegrated circuit (IC) chips. In order to obtain better capacitanceuniformity, a thickness of the insulating layer is increased therebycausing a small capacitance for the resulting capacitor. Ahorizontally-oriented capacitor is able to improve capacitanceuniformity while maintaining a thin insulating layer relative to avertically-oriented capacitor. The relatively thin insulating layerhelps to maintain a small size of the IC chips. A continuous poly onoxide definition edge (CPODE) pattern is used to form a trench byremoving a dummy structure and a portion of a substrate under the dummystructure. In at least one example, the term “oxide definition” is anactive region for a transistor, i.e., the area where a source, a drain,and a channel under a gate of the transistor are formed. In someexamples, the oxide definition region is between insulating regions. Thetrench is filled with a dielectric material usable to form ahorizontally-oriented capacitor. Conductive features of the capacitorare a source/drain electrode of a first transistor and a source/drainelectrode of an adjacent transistor. The horizontally-oriented capacitoroccupies a reduced area in the IC chip while maintaining a uniformcapacitance in comparison with other approaches.

In some embodiments, the insulating regions are called inactive regionsor isolation regions. In some embodiments, the insulating regions areshallow trench isolation (STI), field oxide (FOX) areas, or othersuitable electrically insulating structures. In some embodiments, thecapacitor is aligned with a middle line between two abutted activeregions or two abutted standard cells in the substrate. The two abuttedactive regions or two abutted standard cells are separated by theinsulating layer of the capacitor. In at least one embodiment, thecapacitor is coupled to two transistors. In some embodiments, aplurality of capacitors is between adjacent transistors. In someembodiments, the transistor is a fin field effect transistor (FinFET).In some embodiments, the transistor is a planar field effect transistor.The capacitor and the transistor are included in a complimentarymetal-oxide-semiconductor (CMOS) IC, a memory cell or other similarstructure in some embodiments.

FIG. 1 is a flowchart of a method 100 of fabricating a semiconductordevice including a capacitor in accordance with one or more embodiments.Method 100 includes operation 110 in which a dummy structure is formedover a substrate and spacers are formed along sidewalls of the dummystructure. The dummy structure is on a top surface of the substrate. Inat least one embodiment, a semiconductor strip is formed above thesubstrate and the dummy structure is on a top surface of thesemiconductor strip. In some embodiments, the dummy structure is formedon an edge of a cell. The dummy structure is called a sacrificial gatestructure, in some instances.

The spacers are on the top surface of the substrate. The spacers adjoinsidewalls of the dummy structure. In some embodiments, the spacersinclude silicon oxide, silicon nitride, or another suitable material.For example, the spacers include an oxide-nitride-oxide (ONO) structurein some embodiments.

FIGS. 2A to 2H are schematic cross-section views of the semiconductordevice at various stages of fabrication according to the flowchart ofFIG. 1 in accordance with one or more embodiments.

FIG. 2A is a cross-sectional view of a semiconductor device 200following operation 110 in accordance with one or more embodiments.Semiconductor device 200 includes a substrate 202. In at least oneembodiment, substrate 202 is a silicon substrate. In some embodiments,substrate 202 is a silicon on insulating layer (SOI) substrate, or asilicon on sapphire (SOS) substrate. Substrate 202 includes a suitableelemental semiconductor, such as germanium or diamond; a suitablecompound semiconductor, such as silicon carbide, gallium nitride,gallium arsenide, or indium phosphide; or a suitable alloysemiconductor, such as silicon germanium, silicon tin, aluminum galliumarsenide, or gallium arsenide phosphide.

Insulating regions 204 are located in substrate 202. Active region 206is between insulating regions 204. Active region 206 includes a firstwell region 206A and a second well region 206B. In some embodiments,active region 206 includes a single well region. Dummy gate structures208, 210A, 212A, 210B and 212B are on a top surface of substrate 202. Ina subsequent procedure, dummy gate structures 210A and 210B are replacedwith functioning gate structures. Dummy gate structures 212A and 212Beither remain non-functioning gate structures or are replaced withdifferent non-functioning gate structures. Dummy gate structures 208,210A, 212A, 210B and 212B are at least partially on active region 206.Dummy gate structures 208, 210A and 210B are completely on active region206. Dummy gate structures 212A and 212B are partially on active region206 and partially on insulating regions 204. In some embodiments, dummygate structures 212A and 212B are completely on active region 206. Dummygate structure 210A is on first well region 206A and dummy gatestructure 210B is on second well region 206B. Gate spacers 214 are alongsidewalls of each of dummy gate structures 208, 210A, 212A, 210B and212B.

Insulating regions 204, for example, STI or FOX insulating regions,surround active region 206. A top surface of active region 206 is abovea top surface of insulating regions 204. In some embodiments, the topsurface of active region 206 is substantially coplanar with the topsurface of insulating regions 204. In some embodiments, active region206 is a semiconductor strip between insulating regions 204. Activeregion 206 includes first well region 206A and second well region 206Bdisposed in substrate 202 and adjacent to insulating regions 204. Theformation of the active region 206 (also referred to as a well region)includes an implantation process in some embodiments. Insulating regions204 electrically isolate first well region 206A and second well region206B from other areas of substrate 202. In at least one example, theformation of insulating regions 204 includes a photolithography process,an etch process to form trenches in substrate 202, and a depositionprocess to fill the trenches with one or more dielectric materials. Insome embodiments, the formation of insulating regions 204 includesanother STI procedure or local oxidation of silicon (LOCOS).

Dummy gate structures 208, 210A, 212A, 210B and 212B are on substrate202. In some embodiments, semiconductor device 200 includes dummystructures other than dummy gate structures, such as a dummy structurecompletely on insulating region 204. Dummy gate structure 208 is betweendummy gate structures 210A and dummy gate structures 210B. In someembodiments, in a first transistor, dummy gate structure 210A isreplaceable to form a gate electrode, e.g., in a gate last process; anddummy gate structure 212A and dummy gate structure 208 are subsequentlyusable to form edge gate structures. In the given embodiment, in asecond transistor, dummy gate structure 210B is replaceable to form agate electrode and dummy gate structure 212B and dummy gate structure208 are subsequently usable to form edge gate structures.

In some embodiments, dummy gate structure 212A, dummy gate structure212B, and dummy gate structure 208 do not function as a gate terminal ofactive transistors, but are used to protect an edge of an activetransistor. In at least one example, dummy gate structure 208 is acommon edge gate structure of the first transistor and the secondtransistor. In some embodiments, because dummy gate structure 208 isformed on an edge of an oxide definition (OD) region or an edge of acell, dummy gate structure 208 corresponds to a CPODE pattern. Forexample, dummy gate structure 208 is on two abutted OD regions andaligned with a middle line (i.e., the common edge) of the two abutted ODregions. With respect to FIG. 2A, the two abutted OD regions are firstwell region 206A and second well region 206B. In some embodiments, dummygate structure 208 is offset from the middle line of two abutted ODregions. In some embodiments, in an IC layout, the CPODE pattern isschematically illustrated in drawings with the label “CPODE.” In someembodiments, one or more CPODE patterns are formed of a same material,by using a same photomask, such as poly (polysilicon) patterns. In suchembodiments, the poly patterns and the CPODE patterns are formed in asame layer. In some embodiments, CPODE patterns are merged with one ormore transistors in a standard cell layout to achieve a higher densityand smaller corner variations such as mobility variations caused byprocess variations for cells placed at different locations on a samechip or for chips placed at different locations on a same wafer. Cornervariations are the result of non-uniformities in a manufacturing processwhich result in devices having variations in performancecharacteristics.

Dummy gate structure 208 is between a source/drain feature of the firsttransistor and a source/drain feature of the second transistor.Therefore, a capacitor is formable using dummy gate structure 208 andthe conductive source/drain features of the first and secondtransistors.

In some embodiments, dummy gate structures 208, 210A, 212A, 210B and212B are formed simultaneously. In a “gate last” or “replacement gate”methodology, dummy gate structures 208, 210A, 212A, 210B and 212B, alsocalled sacrificial gate structures, are initially formed, variousprocesses associated with semiconductor device 200 are performed, anddummy gate structures 208, 210A, 212A, 210B and 212B are subsequentlyremoved and replaced with one or more materials. In some embodiments,dummy gate structures 208, 210A, 212A, 210B and 212B include a gatedielectric and/or a gate electrode.

For example, the gate dielectric is silicon dioxide. The silicon dioxideis a thermally grown oxide in some embodiments. In some embodiments, thegate dielectric is a high dielectric constant (high-k) dielectricmaterial. A high-k dielectric material has a dielectric constant higherthan that of silicon dioxide. In some embodiments, the gate electrodeincludes polycrystalline-silicon (poly-Si), poly-crystallinesilicon-germanium (poly-SiGe), metallic nitride, metallic silicide,metallic oxide, metal, and/or other suitable layers. The formation ofthe gate electrode includes a deposition process and a subsequent etchprocess in some embodiments. In some embodiments, dummy gate structures208, 210A, 212A, 210B and 212B further include a hard mask layer on thegate electrode. In some embodiments, dummy gate structures 208, 210A,212A, 210B and 212B are formed in a “gate first” methodology or a hybridprocess of “gate last” and “gate first” methodologies.

Gate spacers 214 are along sidewalls of dummy gate structures 208, 210A,212A, 210B and 212B. Gate spacers 214 include a dielectric material suchas silicon oxide, silicon nitride, silicon oxynitride, silicon carbide,or combinations thereof. The formation of gate spacers 214 includes aprocedure including deposition and etch back processes in someembodiments. In various embodiments, gate spacers 214 are patterned byperforming an isotropic or an anisotropic etch process.

Returning to FIG. 1, method 100 continues with operation 120 in whichconductive features are formed on opposite sides of the dummy gatestructure. Portions of the substrate are removed to form recessesadjacent to the gate spacers. In some embodiments, portions of thesemiconductor strip are removed to form the recesses and the recessesare over the substrate. In some embodiments, the recesses extend throughthe semiconductor strip into the substrate. In some embodiments, therecesses are entirely within the semiconductor strip. The semiconductorstrip is called a fin, in some instances. A filling process is thenperformed by filling the recesses with one or more semiconductormaterials. The formation of the recesses includes an etch process suchas a wet etching or a dry etching. In some embodiments, the etch processis performed to remove a top surface portion of the active regionadjacent to the dummy gate structure and/or the isolation region. Insome embodiments, the filling process is performed by an epitaxial (epi)process. In some embodiments, the conductive features are formed usingan implantation process. In some embodiments, the conductive featuresinclude lightly doped drain (LDD) regions.

FIG. 2B is a cross-sectional view of semiconductor device 200 duringoperation 120 in accordance with one or more embodiments. Recesses 216are in substrate 202 between gate spacers 214 of adjacent dummy gatestructures 208, 210A, 212A, 210B and 212B. In some embodiments, recesses216 are in substrate 202 between gate spacer 214 and insulating region204. Recesses 216 have a substantially triangle, trapezoid, pentagon, orhexagon shape depending on parameters of the etch process used to formrecesses 216 and/or a crystal structure of the substrate 202. Portionsof substrate 202 are removed by an isotropic or an anisotropic etchprocess. The etch process selectively etches substrate 202 withoutetching dummy gate structures 208, 210A, 212A, 210B, 212B and gatespacers 214. In at least one example, a portion of recess 216 extends adistance under gate spacer 214 or a distance under gate structures 208,210A, 212A, 210B and 212B. In some embodiments, the etch process isperformed using a reactive ion etching (RIE), a wet etching, or othersuitable techniques.

FIG. 2C is a cross-sectional view of semiconductor device 200 followingoperation 120 in accordance with one or more embodiments. Conductivefeatures 217A, 218A, 217B, and 218B are in recesses 216. In someembodiments, an epi process is performed to form conductive features217A, 218A, 217B, and 218B. The epi process includes a selective epitaxygrowth (SEG), a chemical vapor deposition (CVD) techniques (e.g.,vapor-phase epitaxy (VPE) and/or ultra-high vacuum CVD (UHV-CVD)),molecular beam epitaxy (MBE), other suitable processes, or combinationsthereof. In some embodiments, the epi process uses gaseous and/or liquidprecursors, which interacts with a composition of substrate 202. In someembodiments, for example, if the first transistor is an n-typetransistor and the second transistor is a p-type transistor, the epiprocess is performed separately for the first transistor and the secondtransistor; or the epi process is performed merely for the firsttransistor or the second transistor. In some embodiments, conductivefeatures 217A, 218A, 217B, and 218B are in-situ doped or undoped duringthe epi process. When undoped during the epi process, conductivefeatures 217A, 218A, 217B, and 218B are doped during a subsequentprocess, in some instances. The doping process is performed by an ionimplantation process, plasma immersion ion implantation (PIII) process,gas and/or solid source diffusion process, other suitable process, orcombinations thereof. In some embodiments, conductive features 217A,218A, 217B, and 218B are further exposed to an annealing process, suchas a rapid thermal annealing process, to diffuse dopants in conductivefeatures 217A, 218A, 217B and 218B. One or more gate spacers, such as anadditional gate spacer that covers gate spacers 212, are formed beforeor after the formation of conductive features 217A, 218A, 217B, and218B, in some instances. In some embodiments, the additional gatespacers include second spacers along sidewalls of gate spacers 212. Forexample, the second spacers are formed by depositing a dielectric layersuch as silicon nitride, silicon oxide, or silicon oxynitride andsubsequently removed by an anisotropic etch process to form a D-shape ora spacer shape.

In at least one embodiment, dummy gate structure 210A is a gate terminalof a first transistor 220A; and conductive features 217A and 218A aresource/drain terminals of the first transistor 220A. Dummy gatestructure 210B is a gate terminal of a second transistor 220B; andconductive features 217B and 218B are source/drain terminals of thesecond transistor 220B. Conductive features 217A, 218A, 217B, and 218Bextend above the top surface of substrate 202 and are referred to asraised source and drain regions, in some instances. A pair of adjacentconductive features is able to function as two conductive components ina capacitor. For example, conductive features 218A and 217B with aninsulator therebetween form a capacitor.

Returning again to FIG. 1, method 100 continues with operation 130 inwhich a dielectric layer is deposited over the dummy gate structure andthe conductive features. In some embodiments, an etch stop layer such asa contact etch stop layer (CESL) is deposited on the dummy gatestructures and the conductive features prior to depositing thedielectric layer. The etch stop layer includes silicon oxide, siliconnitride, silicon oxynitride, silicon carbide, silicon oxycarbide, orother suitable material. In some embodiments, the formation of the etchstop layer includes a deposition process and then an etch back process.The etch stop layer is deposited by CVD, high density plasma CVD(HDP-CVD), spin-on coating, physical vapor deposition (PVD), atomiclayer deposition (ALD), and/or other suitable method. Afterward, forexample, a dielectric layer is deposited by CVD, PVD, high densityplasma (HDP), spin-on-dielectric process, other suitable processes,and/or combination thereof. In some embodiments, the deposition processis followed by a planarization process, such as a chemical mechanicalpolishing (CMP) process, an etch process, or another suitable process.

FIG. 2D is a cross-sectional view of semiconductor device 200 followingoperation 130 in accordance with one or more embodiments. After an etchstop layer (not shown) is formed over dummy gate structures 208, 210A,212A, 210B and 212B, gate spacers 214, and conductive features 217A,218A, 217B and 218B, an inter-layer dielectric (ILD) 222 is depositedover the etch stop layer. In some embodiments, ILD 222 includes aninsulating material such as silicon oxide, silicon nitride, undopedsilicate glass (USG), Boro-Silicate Glass (BSG), a low-k material, TEOS,other suitable materials, and/or combination thereof. In someembodiments, ILD 222 is planarized to be coplanar with a top surface ofdummy gate structures 208, 210A, 212A, 210B and 212B. For example, ILD222 is planarized by using a chemical mechanical planarization (CMP) toremove portions of ILD 222 over dummy gate structures 208, 212A and 212Bas well as dummy gate structures 210A and 210B. In some embodiments, theCMP is applied to remove the etch stop layer on the dummy gatestructures 208, 210A, 212A, 210B and 212B to expose the gate electrode.In some embodiments, the CMP is applied to further remove the hard masklayer on the gate electrode. In various embodiments, other planarizationtechniques are used, such as an etch process.

Returning again to FIG. 1, method 100 continues with operation 140 inwhich the dummy gate structure is removed from the substrate. In someembodiments, the dummy gate structure is the common dummy gate betweenthe first active region and the second active region. The dummy gatestructure is removed using a photolithography process and an etchprocess. During the photolithography process, the dummy gate structurecorresponding to the CPODE pattern is exposed while the other gatestructures or dummy gate structures are covered by a mask layer. Theetch process is performed to remove the gate dielectric and gateelectrode to expose the top surface of the substrate. In someembodiments, removing the dummy gate structure comprises replacing dummygate structures other than the CPODE pattern dummy gate structure withgate electrodes in a “gate last” process.

FIG. 2E is a cross-sectional view of semiconductor device 200 duringoperation 140 in accordance with one or more embodiments. FIG. 2E is across-sectional view during a “gate last” process in which dummy gatestructures 210A, 212A, 210B and 212B are removed to be replaced by gateelectrodes. The gate electrode and gate dielectric are removed fromdummy gate structures 210A, 212A, 210B, and 212B, resulting in openings224 in ILD 222. Openings 224 are between gate spacers 214. Removal ofthe gate electrode and gate dielectrics from dummy gate structures 210A,212A, 210B, and 212B includes a photolithography process and an etchprocess. The etch process includes a wet etching by using a solutionsuch as NH₄OH, dilute HF, and/or other suitable etchant, or a dryetching by using a gas such as fluorine-based and/or chlorine-basedetchants. In some embodiments, the gate dielectric remains on the topsurface of substrate 202 and only the gate electrode is removed. Forexample, the gate dielectric is a high-k dielectric material such asHfO₂, TiO₂, HfZrO, Ta₂O₃, HfSiO₄, ZrO₂, ZrSiO₂, and/or other suitablematerials. In at least one embodiment, the gate dielectric issubsequently removed from substrate 202 by using a buffered oxideetchant (BOE) after the removal of the gate electrode. A gatereplacement process is then performed. In some embodiments, openings 224are filled with one or more layers. For example, a first dielectriclayer is formed on the top surface of substrate 202 by using a thermaloxidation process. The first dielectric layer is formed by a depositionprocess, in some instances. In some embodiments, a second dielectriclayer is formed on the first dielectric layer. The second dielectriclayer includes a high-k dielectric material, in some instances. In someembodiments, the second dielectric layer has a U-shape or a rectangularshape. In some embodiments, a conductive layer is located within acavity defined by the second dielectric layer. The conductive layer isdisposed directly on the first dielectric layer, in some instances. Inat least one embodiment, the conductive layer is tungsten. In someembodiments, the conductive layer includes different materials such astitanium, nickel, or tantalum, and has a work function suitable for ap-type device or an n-type device. In first transistor 220A, a gateelectrode and an edge gate structure are formed after the gatereplacement process. In second transistor 220B, a gate structure and adummy gate structure are formed after the gate replacement process.

Returning again to FIG. 1, method 100 continues with operation 150 inwhich a portion of the substrate under the dummy structure is removed toform a trench. The dummy gate structure and the portion of the substrateunderneath are removed using one or multiple etch processes. In someembodiments, a removal process used to remove the dummy structure inoperation 140 and a removal process used to remove a portion of thesubstrate in operation 150 is a continuous removal process. In someembodiments, the removal process used to remove the dummy structure inoperation 140 and the removal process used to remove the portion of thesubstrate in operation 150 are separate removal processes. In at leastone embodiment, the trench corresponds to the CPODE pattern. In someembodiments, the trench separates the two abutted active regions. Insome embodiments, the trench is between two abutted standard cells. Thetrench extends through at least the abutted two well regions of the twoabutted active regions, i.e., a bottom surface of the trench is below abottom surface of the abutted two well regions. The formation of thetrench includes an etch process. During the etch process, at least aportion of the substrate is removed to define a trench between theneighboring active regions. In some embodiments, such etch process iscalled over etching.

FIG. 2F is a cross-sectional view of semiconductor device 200 followingoperation 150 in accordance with one or more embodiments. A trench 230includes an upper portion 230A and a lower portion 230B. Upper portion230A is above the top surface of substrate 202 and lower portion 230B isbelow the top surface of substrate 202. Upper portion 230A is similar toopenings 224 of gate structures 226A, 228A, 226B, and 228B. In someembodiments, upper portion 230A is formed simultaneously with theformation of openings 224. In some embodiments, upper portion 230A isformed sequentially with the formation of openings 224. Lower portion230B is aligned with upper portion 230A. In some embodiments, upperportion 230A and lower portion 230B are formed by a single etch process.In some embodiments upper portion 230A and lower portion 230B are formedby multiple etch processes. For example, upper portion 230A is removedby the same procedure as openings 224 and lower portion 230B is removedby a subsequent dry etching with a plasma source and an etchant gas. Theplasma source may be an inductively coupled plasma (ICP), a transformercoupled plasma (TCP), an electron cyclotron resonance (ECR), a RIE,and/or other suitable techniques. In at least one embodiment, trench 230separates one active region into two active regions such as first wellregion 206A and second well region 206B. To reduce or prevent a leakagecurrent between first transistor 220A and second transistor 220B, trench230 extends to a depth equal to or greater than a depth of well regions.In some embodiments, adjacent conductive features 218A and 217B are atleast partially exposed by trench 230. In some embodiments, an entiresidewall of conductive features 218A and 217B are exposed by trench 230.In some embodiments, portions of adjacent conductive features 218A and217B are removed during the removal process to form lower portion 230B.

Returning again to FIG. 1, method 100 continues with operation 160 inwhich the trench is filled with a dielectric material. In someembodiments, the trench is filled with more than one dielectricmaterials. The dielectric material is usable as an insulating layer of acapacitor. The dielectric material has a width substantially equal to agate length of the dummy structure and the other gate structures. Theformation of the dielectric material includes a deposition process. Insome embodiments, a planarization or etching process is used to removeexcess material deposited during the formation of the dielectricmaterial.

FIG. 2G is a cross-sectional view of semiconductor device 200 followingoperation 160 in accordance with one or more embodiments. Trench 230 isfilled with dielectric material 232. In some embodiments, dielectricmaterial 232 is silicon nitride, or silicon dioxide. In someembodiments, a top surface of dielectric material 232 is substantiallyco-planar with a top surface of gate structure 226A, 228A, 226B, or228B. In some embodiments, a width of dielectric material 232 issubstantially the same as the gate length of at least one of gatestructure 226A, 228A, 226B, or 228B. The width of dielectric material232 ranges from about 40 Angstroms (Å) to about 200 Å depending on aprocess node of semiconductor device 200. For example, the width ofdielectric material 232 ranges from about 60 Å to about 100 Å, in someembodiments. If the width of dielectric material 232 is too thick, acapacitance of a capacitor 234 will be too small to increasefunctionality of semiconductor device 200, in some instances. If thewidth of dielectric material 232 is too thin, the dielectric materialwill not effectively insulate conductive feature 218A from conductivefeature 217B, in some instances. Dielectric material 232 contactsconductive features 218A and 217B. In some embodiments, dielectricmaterial 232 includes multiple structures. For example, dielectricmaterial 232 includes an oxide-nitride-oxide structure (ONO). In someembodiments, upper portion 230A of trench 230 is filled with onedielectric material, and lower portion 230B of trench 230 is filled withone different dielectric material. Dielectric material 232 is formed byusing a deposition process such as CVD, PVD, ALD, and/or other suitableprocesses, and/or combination thereof. In some embodiments, a firstformation process is used to fill upper portion 230A and a differentformation process is used to fill lower portion 230B. Dielectricmaterial 232, conductive feature 218A, and conductive feature 217B formcapacitor 234 wherein dielectric material 232 is an insulating layerbetween two conductive components 218A and 217B. In some embodiments,one or more capacitors are formed between conductive feature 218A andconductive feature 217B. In some embodiments, dummy gate structures210A, 212A, 210B and 212B are able to be replaced after the formation ofthe dielectric material 232.

In comparison with other approaches which do not use a CPODE layer toform an insulating layer of a capacitor, capacitor 234 includes agreater capacitance with a thin and uniform dielectric material 232.Because dielectric material 232 occupies a small area, capacitor 234 isable to achieve a high capacitance per unit area. In additional,capacitor 234 is able to be coupled to a transistor in an IC layoutarrangement without added considerations directed to the priority ofcapacitors and preserving additional areas to achieve sufficientcapacitance. For example, capacitor 234 and transistors 220A and 220Bare included in a layout unit configured to be a standard cell in a maskdesign. Moreover, in comparison with other approaches which do not usesource/drain features as conductive components of a capacitor, capacitor234 reduces a manufacturing cost because additional photomasks andmanufacturing processes are avoided by forming capacitor 234 along withformation of transistors. For example, additional steps formanufacturing metal plates in areas such as interconnect structures areavoided. Meanwhile, because dielectric material 232 is in trench 230, arisk of misalignment is reduced or completely avoided during thefabrication of capacitor 234.

FIG. 2H is a cross-sectional view of semiconductor device 200 followingoperation 150 in accordance with one or more embodiments. Contactstructures 234 are formed on conductive features 217A, 218A, 217B, and218B. Semiconductor device 200 includes first transistor 220A, secondtransistor 220B, and capacitor 234. A plurality of contact openings (notshown) are formed in ILD 222 to expose conductive features 217A, 218A,217B, and 218B. Contact structures 236 extend through ILD 222 and fillthe contact openings. Contact structures 236 electrically connect toconductive features 217A, 218A, 217B, and 218B. For example, contactstructure 236 electrically connects to a silicide formed on a topsurface of conductive features. In some embodiments, contact structure236 includes a contact plug and a liner. The contact plug is laterallysurrounded by the liner. The liner is deposited in contact openingbefore the fabrication of the contact plug. In some embodiments, theliner is formed using CVD or other suitable processes, and/orcombination thereof. One or more films are formed between the contactopening and contact structure 236, in some instances. In one or moreembodiments, the liner is formed of titanium nitride, tungsten nitride,suitable nitride, or other materials. In some embodiments, contactstructure 236 is coupled to another device or component of substrate202.

FIG. 3A is a schematic diagram of a semiconductor device 300 inaccordance with one or more embodiments. Semiconductor device 300includes a transistor 320A, a capacitor 334, a word line WL, a bit lineBL, and a reference voltage node Vref. In some embodiments,semiconductor device 300 is a memory cell. For example, such memory cellis called one transistor-one capacitor (1T1C) dynamic random accessmemory (DRAM), in some instances. A first transistor 320A includes agate node, i.e., a gate structure 326A, source/drain nodes, i.e.,conductive features 317A/318A, where conductive feature 318A iselectrically coupled to capacitor 334.

FIG. 3B is a cross-sectional view of semiconductor device 300. Capacitor334 is electrically coupled to first transistor 320A and a secondtransistor 320B. Conductive feature 318A is a source electrode or adrain electrode of first transistor 320A, and is also a conductivecomponent of capacitor 334. Conductive feature 317B is a sourceelectrode or a drain electrode of second transistor 320B, and is alsothe other conductive component of capacitor 334.

In some embodiments, second transistor 320B is inactive so that firsttransistor 320A and capacitor 334 form a 1T1C memory cell. For example,in first transistor 320A, conductive feature 317A is coupled to bit lineBL through a contact structure 336 and gate structure 326A is coupled toword line WL, where word line WL is called a control line because wordline WL provides a control signal for accessing the memory cell. Firsttransistor 320A is also called an access transistor in the memory cell.Conductive feature 318A acts as a node between first transistor 320A andcapacitor 334. The other node of capacitor 334, i.e., conductive feature317B, is coupled to reference voltage node Vref. In at least oneembodiment, reference voltage node Vref is ground. In one or moreembodiments, the couplings to word line WL, bit line BL, and referencevoltage node Vref are completed in the subsequent metal wiring process.

FIG. 4A is a schematic diagram of a semiconductor device 400 inaccordance with one or more embodiments. Semiconductor device 400includes a first transistor 420A, a second transistor 420B, a firstcapacitor 434A, a second capacitor 434B, a word line WL, a bit line BL,a bit line bar BLB, and a plate line PL. In some embodiments,semiconductor device 400 is a memory cell. For example, such memory cellis called two transistor-two capacitor (2T2C) DRAM. A first transistor420A includes a gate node, i.e., a gate structure 426A, source/drainnodes, i.e., conductive features 417A/418A, where conductive feature418A is electrically coupled to first capacitor 434A. A secondtransistor 420B includes a gate node, i.e., a gate structure 426B,source/drain nodes, i.e., conductive features 417B/418B, whereconductive feature 417B is electrically coupled to second capacitor434B.

FIG. 4B is a cross-sectional view of semiconductor device 400, firstcapacitor 434A is electrically coupled to first transistor 420A and acommon conductive feature 419. Conductive feature 418A is a sourceelectrode or a drain electrode of first transistor 420A, and is also aconductive component of first capacitor 434A. Second capacitor 434B iselectrically coupled to second transistor 420B and common conductivefeature 419. Conductive feature 417B is a source electrode or a drainelectrode of second transistor 420B and common conductive feature 419.In some embodiments, common conductive feature 419 is formed using thesame procedure as conductive features 417A, 418A, 417B, and 418B. Insome embodiments, more capacitors are able to be coupled in seriesbetween first transistor 420A and second transistor 420B.

In some embodiments, in first transistor 420A, conductive feature 417Ais coupled to bit line BL through a contact structure 436 and gatestructure 426A is coupled to word line WL where word line WL is called acontrol line. Conductive feature 418A is a node between first transistor420A and first capacitor 434A. In some embodiments, in second transistor420B, conductive feature 418B is coupled to bit line BLB through contactstructure 436 and gate structure 426B is coupled to word line WL.Conductive feature 417B is a node between second transistor 420B andsecond capacitor 434B. Common conductive feature 419 is a commonconductive component of first capacitor 434A and second capacitor 434B.In some embodiments, common conductive feature 419 is coupled to plateline PL. Plate line PL is called a reference voltage node or a groundvoltage, in some instances. In one or more embodiments, the couplings toword line WL, bit line BL, bit line bar BLB, and plate line PL arecompleted in the subsequent metal wiring process. The couplings of the2T2C memory structure are able to be modified to realize various formsof 2T2C memory structure depending on design requirements.

Semiconductor devices 200, 300, and 400 may undergo further processingto complete fabrication. For example, a not-illustrated multilayerinterconnection (MLI) including metal layers (e.g., M1, M2, etc.) andinter-metal dielectric (IMD) are formed above gate structures224A/226A/224B/226B, 326A/326B, and 426A/426B and conductive features217A/218A/217B/218B, 317A/318A/317B/318B, and 417A/418A/417B/418B/419 inorder to electrically couple various device parts to form an IC. Themultilayer interconnection includes vertical interconnects, such as viasor contact structures, and horizontal interconnects, such as metallines. In some embodiment, the various interconnection features utilizevarious conductive materials including copper, aluminum, tungsten, andsilicide.

One aspect of this description relates to a method of fabricating asemiconductor device. The method includes forming a dummy structure overa substrate, forming conductive features on opposite sides of the dummygate structure, removing the dummy structure and a portion of thesubstrate beneath the dummy gate structure to form a trench, and fillingthe trench with a dielectric material.

Another aspect of this description relates to a method of fabricating acapacitor. The method includes forming a dummy gate structure over asubstrate, wherein the dummy gate structure is an edge gate structurebetween a source/drain electrode of a first transistor and asource/drain electrode of a second transistor, removing the dummy gatestructure to define a first trench, removing a portion of the substrateexposed by the first trench to form a second trench aligned with thefirst trench, filling the first trench with a first dielectric material,and filling the second trench with a second dielectric material.

Still another aspect of this description relates to a semiconductordevice. The semiconductor device includes a substrate, a firsttransistor on the substrate, wherein the first transistor comprises afirst source/drain electrode, a second transistor on the substrate,wherein the second transistor comprises a second source/drain electrode,and an insulating layer extending into the substrate. The insulatinglayer directly contacts the first source/drain electrode and the secondsource/drain electrode, and the insulating layer is between the firstsource/drain electrode and the second source/drain electrode in adirection parallel to a top surface of the substrate.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the embodiments as defined by the appended claims. Moreover,the scope of the present application is not intended to be limited tothe particular embodiments of the process, machine, manufacture, andcomposition of matter, means, methods, operations, and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, operations, or steps, presentlyexisting or later to be developed, that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized according to thedisclosure. Accordingly, the appended claims are intended to includewithin their scope such processes, machines, manufacture, compositionsof matter, means, methods, operations, or steps. In addition, each claimconstitutes a separate embodiment, and the combination of various claimsand embodiments are within the scope of the disclosure.

1. A method of fabricating a semiconductor device, the methodcomprising: forming a dummy structure over a substrate; formingconductive features on opposite sides of the dummy structure; removingthe dummy structure and a portion of the substrate beneath the dummystructure to form a trench, wherein removing the portion of thesubstrate exposes a portion of the conductive features; and filling thetrench with a dielectric material.
 2. (canceled)
 3. The method of claim1, wherein the dielectric material and the conductive features form acapacitor.
 4. The method of claim 1, wherein removing the portion of thesubstrate comprises etching through an active layer to isolate a firstwell region and a second well region at opposite sides of the trench. 5.The method of claim 1, wherein removing the dummy structure and theportion of the substrate comprises defining the trench comprising anupper portion above a top surface of the substrate and a lower portionbelow the top surface of the substrate, and the upper portion is alignedwith the lower portion.
 6. The method of claim 1, wherein removing thedummy structure and the portion of the substrate comprises defining thetrench having a width ranging from about 40 angstroms (Å) to about 200Å.
 7. A method of fabricating a semiconductor device, the methodcomprising: forming a dummy gate structure over a substrate, wherein thedummy gate structure is an edge gate structure between a source/drainelectrode of a first transistor and a source/drain electrode of a secondtransistor; removing the dummy gate structure to define a first trench;removing a portion of the substrate exposed by the first trench to forma second trench aligned with the first trench; filling the first trenchwith a first dielectric material; and filling the second trench with asecond dielectric material different from the first dielectric material.8. (canceled)
 9. The method of claim 7, wherein removing the portion ofthe substrate comprises removing the portion of the substrate andremoving the dummy gate structure in a single etch process.
 10. Themethod of claim 7, wherein filling the first trench with the firstdielectric material comprises filling the first trench with siliconnitride.
 11. The method of claim 7, further comprising: connecting agate of the first transistor to a word line; and connecting thesource/drain electrode of the second transistor to a reference voltage.12. The method of claim 11, further comprising connecting an additionalsource/drain electrode of the first transistor to a bit line, whereinthe gate of the first transistor is between the additional source/drainelectrode and the first dielectric material.
 13. The method of claim 12,wherein removing the portion of the substrate comprises defining thesecond trench having a bottom surface lower than a bottom surface of awell in the substrate.
 14. The method of claim 13, wherein filling thefirst trench with the first dielectric material comprises planarizingthe first dielectric material to form a top surface of the firstdielectric material co-planar with a top surface of the gate of thefirst transistor.
 15. The method of claim 14, wherein removing the dummygate structure comprises forming the first trench having a width rangingfrom about 60 angstroms (Å) to about 100 Å. 16-20. (canceled)
 21. Amethod of manufacturing a semiconductor device, the method comprising:forming a first sacrificial gate structure and a second sacrificial gatestructure over a fin structure, wherein the first sacrificial gatestructure is over a first well region, and the second sacrificial gatestructure is over an interface between the first well region and asecond well region; depositing an insulating material over the firstsacrificial gate structure and the second gate sacrificial structure;removing the first sacrificial gate structure to form a first trench;removing the second sacrificial gate structure to form a second trench;filling the first trench with a conductive material; and filling thesecond trench with a dielectric material.
 22. The method of claim 21,wherein the removing of the first sacrificial gate structure to form thefirst trench comprises: removing the first sacrificial gate structureuntil the fin structure is exposed.
 23. The method of claim 21, whereinthe removing of the second sacrificial gate structure to form the secondtrench comprises: removing the second sacrificial gate structure and aportion of the substrate beneath the second sacrificial gate structure,wherein a bottom surface of the second trench is below a bottom surfaceof the first well region.
 24. The method of claim 21, wherein theremoving of the second sacrificial gate structure to form a secondtrench comprises: using a photomask corresponding to a continuous polyon oxide definition edge (CPODE) pattern to define the secondsacrificial gate structure.
 25. The method of claim 21, wherein theforming of the first sacrificial gate structure and the secondsacrificial gate structure comprises: forming the first sacrificial gatestructure to have a same gate length as that of the second sacrificialgate structure.
 26. The method of claim 1, wherein the filling of thetrench with a dielectric material comprises: filling a first portion ofthe trench with a first dielectric material, and filling a secondportion of the trench with a second dielectric material different fromthe first dielectric material.
 27. The method of claim 1, furthercomprising planarizing the semiconductor device to expose a top surfaceof the dummy structure prior to the removing of the dummy structure.